JP2012148333A - Method for preventing melt and adhesion in consumable electrode arc welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing melt and adhesion which prevents melt and adhesion on completion of welding in consumable electrode arc welding.SOLUTION: In the method for preventing melt and adhesion in consumable electrode arc welding, a stop command is output to a motor when a welding completion command is input to a welding source, and the output of the welding source is antistic-controlled so that a wire kindling height on stop of a welding wire may reach a prescribed value, in a preset melt and adhesion preventing period from the time at which the antistic control is completed, melt and adhesion preventing voltage lower than antistic voltage is output, and, in the melt and adhesion preventing period, external characteristics are formed in which a tilt becomes positive rising properties when short circuit current is less than a preset short circuit standard current value and the tilt becomes zero and negative flat properties when it is more than the short circuit standard value.

Description

  The present invention relates to control for preventing welding at the end of welding in consumable electrode arc welding.

  In consumable electrode arc welding such as MIG and MAG welding, when the torch is moved after the anti-stick control of welding is completed, the welding wire is often short-circuited to the work piece due to camera shake or the like. To solve this problem, a voltage lower than the anti-stic voltage is output to the welding wire for a predetermined period after the anti-stic control is completed, and when the welding wire is short-circuited and welded to the molten pool of the workpiece, the welding wire is It was released from welding.

  FIG. 4 is an electrical connection diagram of a welding power source for carrying out a welding prevention method for consumable electrode arc welding according to the prior art. In the figure, a main power supply circuit INV performs output control by inverter control with a commercial power supply such as three-phase 200 V as an input, and outputs a welding current and a welding voltage. The output voltage detection circuit VD detects the output voltage of the main power supply circuit INV and outputs it as an output voltage detection signal Vd. The output current detection circuit ID detects the output current of the main power supply circuit INV and outputs it as an output current detection signal Id.

  The output voltage setting circuit VS shown in FIG. 4 outputs a predetermined output voltage setting signal Vs, and the constant voltage characteristic setting circuit CVC outputs a predetermined constant voltage characteristic setting signal Cvc. The external characteristic control circuit SC receives the output voltage setting signal Vs, the constant voltage characteristic setting signal Cvc, and the output current detection signal Id and performs an operation to form an external characteristic of the first constant voltage characteristic L1 shown in FIG. When the characteristic control signal Sc is output and the anti-stick process ends, an anti-stick process end signal At is output.

  The welding prevention period setting circuit MPT outputs a welding prevention period setting signal Mpt for a predetermined period in accordance with the input of the anti-stick process end signal At. When the welding prevention period setting signal Mpt is input, the external characteristic control circuit SC forms the external characteristic of the second constant voltage characteristic L2 obtained by stepping down the first constant voltage characteristic L1 shown in FIG. An external characteristic control signal Sc is output.

  FIG. 5 is a waveform diagram when the welding wire is released from welding by applying a predetermined voltage to the welding wire when the welding wire is short-circuited and welded to the molten pool after the anti-stick treatment of the prior art is completed. 5, (A) shows the output voltage signal Vd, (B) shows the output current signal Id, and (C1) to (C5) show when the welding wire is released from the weld pool. Shows the state. Hereinafter, the operation of the prior art will be described with reference to FIG.

  The external characteristic control circuit SC performs external characteristic control that becomes the second constant voltage characteristic L2 obtained by stepping down the first constant voltage characteristic L1 shown in FIG. 3 in response to the input of the welding prevention period setting signal Mpt. For example, when the load voltage is 20V, the voltage is stepped down to 14V.

  At time t = t1 during the welding prevention period, when the welding torch 4 is moved to a predetermined position, the welding wire 1 is short-circuited to the workpiece 2 for a long time due to camera shake or the like, and is strongly welded. The output current detection signal Id shown in FIG. 3 gradually increases, and the output voltage detection signal Id shown in FIG. 3A becomes a low value of about several volts because it is in a short circuit state, and at time t = t2, the output current detection signal Id When the value of Id becomes larger than a predetermined reference current value, an arc is generated as shown in FIG.

  By pulling up the welding wire 1 from the workpiece 2 in a state where an arc is generated, the welding wire 1 is detached from the molten pool of the workpiece 2 at time t = t3. At time t = t4, when the arc length is further increased, the arc is extinguished. At this time, for example, the operating point of the second constant voltage characteristic 12 shown in FIG. 3 moves from the point C to the point A, and the value of the output voltage detection signal Id shown in FIG. Increase for ~ t4.

  Even if the welding wire 1 is short-circuited to the workpiece 2 again and is weakly welded while the welding torch 4 is moving at the time t = t4 to t5, the output current detection signal Id is rapidly changed as shown in FIG. Then, at time t = t6, when the value of the output current detection signal Id becomes larger than a predetermined reference current value, an arc is generated as shown in FIG. At this time, a short-circuit current similar to that of a long short circuit flows despite a short short circuit.

  The welding wire 1 is detached from the molten pool of the workpiece 2 by pulling the welding wire 1 again from the workpiece 2 while the arc is generated. At time t = t7, when the arc length is further increased, the arc is extinguished.

  In the above description, regardless of the length of the short-circuit between the welding wire 1 and the workpiece 2, the current rising speed at the initial stage of the short-circuit is fast. When the workpiece 2 leaves the molten pool, a lot of spatter is generated, and a lot of spatter adheres to the workpiece, resulting in poor welding.

  In the output control method of the pulse arc welding power supply device described in Patent Document 1, it is described that external characteristics are controlled.

JP 2002-283050 A

  In the consumable electrode type arc welding, when the welding torch is moved immediately after the anti-stick control is completed, the tip of the welding wire is often short-circuited to the molten pool of the workpiece due to camera shake or the like and is often welded. In order to prevent this problem, conventionally, when the anti-stick control is applied to the welding wire for a predetermined period immediately after the anti-stick control is completed to prevent welding, and the welding wire is welded to the workpiece, the welding wire Was unwelding.

  However, the short-circuiting of the moving welding wire may cause a short-circuit state of a long short-circuit or a short-circuit, resulting in strong welding and light welding. At this time, in the conventional welding prevention method, a large short-circuit current flows even when weakly welded by a short circuit, so when the welding wire is separated from the molten pool of the workpiece, a lot of spatter occurs and discharge traces are formed on the workpiece. It will adhere to and cause poor welding.

  Therefore, an object of the present invention is to provide a welding prevention method in which spatter is hardly generated when the welding wire is detached from the molten pool of the workpiece regardless of the short-circuit state of the welding wire.

  In order to solve the above-described problem, the invention of claim 1 outputs a stop command to the motor when a welding end command is input to the welding power source, and the wire burn-up height when the welding wire stops becomes a predetermined value. In the method for preventing welding of consumable electrode arc welding in which the output of the welding power source is controlled in an anti-stick manner, a welding prevention voltage lower than the anti-stic voltage is output during a predetermined welding prevention period from the end of the anti-stick control. In the welding prevention period, an external characteristic is formed in which the slope has a positive rising characteristic when the short-circuit current is less than a predetermined short-circuit reference current value, and the slope has zero and negative flat characteristics when the short-circuit current is greater than the short-circuit reference current value. This is a welding prevention method for consumable electrode arc welding.

According to the present invention, the external characteristics of the welding power source during the welding prevention period are formed by the rising characteristics and the flat characteristics, so that when the welding wire is long and strongly welded, the external characteristics become flat characteristics. By controlling and applying a high output voltage to the welding wire, a large current flows at the time of a short circuit, and welding can be easily released even with strong welding. Conversely, when the welding wire is short-circuited and weakly welded, it is possible to melt weak welding with a small current by controlling the external characteristics to be increased and lowering the output voltage applied to the welding wire. The spatter generated when the welding wire is detached from the molten pool of the workpiece can be greatly reduced.
As described above, since the welding prevention voltage applied to the welding wire can be optimized according to the short-circuit state, the spatter generated when the welding wire is released from the welding can be suppressed, leading to improvement in welding quality.

FIG. 2 is an electrical connection diagram of a welding power source for carrying out a welding prevention method for consumable electrode arc welding according to an embodiment of the present invention. It is a wave form diagram explaining operation | movement of embodiment. It is an external characteristic view of an embodiment. FIG. 6 is an electrical connection diagram of a welding power source for carrying out a welding prevention method for consumable electrode arc welding according to the prior art. It is a wave form diagram explaining operation | movement of a prior art.

An embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.
FIG. 1 is an electrical connection diagram of a welding power source for carrying out a welding prevention method for consumable electrode arc welding according to an embodiment of the present invention. In the figure, components having the same reference numerals as those in the electrical connection diagram of the conventional welding power source shown in FIG. 4 perform the same operations, and thus description thereof will be omitted. Only components having different reference numerals will be described.

  The external characteristic inclination setting circuit MPC shown in FIG. 1 outputs a predetermined external characteristic inclination setting signal Mpc. At this time, when the slope of the external characteristic L3 shown in FIG. 3 is a positive increase characteristic, 1V to 3V / 100A is desirable. When the inclination is zero or a negative flat characteristic, 0 V to 3 V / 100 A is desirable.

  The welding prevention period setting circuit MPT shown in FIG. 1 outputs a welding prevention period setting signal Mpt in response to the input of the anti-stick process end signal At. Switching circuit SW switches between constant voltage characteristic setting signal Cvc and external characteristic inclination setting signal Mpc in accordance with welding prevention period setting signal Mpt.

  The external characteristic control circuit SC shown in FIG. 1 outputs an anti-stic process end signal At to the welding prevention period setting circuit MPT when the anti-stick process is completed, and at the same time, an output voltage setting signal Vs and an external characteristic slope setting during the welding prevention period. An external characteristic control signal Sc that performs calculation with the signal Mpc and the output current detection signal Id as inputs and forms an external characteristic in which the slope of the external characteristic L3 shown in FIG. 3 is a positive rising characteristic and the slope is zero or a negative flat characteristic. Is output.

  FIG. 2 is a waveform diagram for explaining the operation of the embodiment of the present invention. In FIG. 2, (A) shows the output voltage signal Vd, (B) shows the output current signal Id, and (C1) to (C5) show that the welding wire is short-circuited and released from the molten pool. Indicates the state when The operation of the embodiment of the present invention will be described below with reference to FIG.

  The switching circuit SW shown in FIG. 1 selects the constant voltage characteristic setting signal Cvc of the contact a when the welding prevention period setting signal Mpt is at the low level, and switches from the contact a to the contact b when the welding prevention period setting signal Mpt is at the high level. Select Mpc.

  When the anti-stick process is completed and the welding wire 1 is short-circuited to the workpiece 2 for a long time due to camera shake or the like when moving the welding torch 4 to a predetermined position at time t = t1 during the welding prevention period shown in FIG. The short circuit control is performed with the positive increase characteristic of the external characteristic L3 shown in FIG.

  In the short circuit at time t = t1 to t2 shown in FIG. 2, the value of the output current detection signal Id shown in FIG. 2B gradually increases according to the positive rise characteristic of the external characteristic L3 shown in FIG. The rising characteristic shifts to a point C having a zero flat characteristic via point B, and an arc is generated at time t = t2. At this time, due to the zero flat characteristic of the external characteristic L3, the value of the output voltage signal Vd in FIG. 3A at time t = t2 to t3 is large, and the burning of the welding wire 1 is large.

When the welding wire 1 is pulled up from the workpiece 2 in this large burn-up state, the welding wire 1 is easily detached from the molten pool of the workpiece 2. Then, at time t = t3, the zero flat characteristic of the external characteristic L3 shown in FIG. 3 returns to the positive ascending characteristic, and when the load is increased by further lifting the welding wire 1 from the workpiece 2, the positive ascending characteristic is obtained. Accordingly, the value of the output current detection signal Id decreases rapidly and the arc is extinguished quickly.
As described above, even if the welding wire 1 is strongly welded to the work piece 2 due to a long short circuit, the welding wire 1 is greatly burned with the zero flat characteristic of the external characteristic L3, so that the welding can be easily released.

  If the welding wire 1 is short-circuited again to the workpiece 2 again at time t = t5 during the movement of the welding torch 4 during the welding prevention period, short-circuit control is performed with the positive increase characteristic of the external characteristic L3 shown in FIG.

  At time t = t5 to t6 shown in FIG. 2, the value of the output current detection signal Id shown in FIG. 2B increases in accordance with the positive increase characteristic of the external characteristic L3 shown in FIG. However, if the short-circuit period is short, short-circuit control is performed with the positive rise characteristic shown in FIG. 3, and an arc is generated with the positive rise characteristic at time t = t6. At this time, due to the positive increase characteristic of the external characteristic L3, an increase in the value of the output current detection signal Id is suppressed, and the burning of the welding wire 1 is reduced.

  When the welding wire 1 is short-circuited and lightly welded to the work piece 2, the welding wire 1 can be released from the welding of the work piece 2 even with a small burn-up, so that spatter generated when releasing the welding can be suppressed. Then, at time t = t6, when the welding wire 1 is further pulled up from the workpiece 2 in the positive increase characteristic region of the external characteristic L3 shown in FIG. 3 and the load is increased, the arc is extinguished quickly.

  As described above, by forming the external characteristics of the welding power source during the welding prevention period with positive rising characteristics and zero flat characteristics, a high welding prevention voltage is applied to the welding wire 1 when the welding wire 1 is strongly welded to the workpiece 2. Can be easily released even by strong welding. Conversely, when the welding wire 1 is weakly welded, a low welding prevention voltage is applied to the welding wire to release the welding, so that spatter generated when the welding wire 1 is detached from the workpiece 2 can be greatly reduced, and welding is performed. It leads to quality improvement.

  In the above description, the external characteristic L3 shown in FIG. 3 is a zero flat characteristic, but may be a negative flat characteristic (for example, 0 V to −3 V / 100 A). Further, in the range of the welding prevention voltage of the external characteristic L3, a range of 10V to 15V is desirable for the positive rising characteristic, and 15V is desirable for the zero flat characteristic. With this value, the welding prevention effect and the sputtering suppression effect are large.

DESCRIPTION OF SYMBOLS 1 Non-consumable electrode 2 Base material 3 Arc 4 Welding torch 5 Motor At Anti-stick process end signal CVC Constant voltage characteristic setting circuit Cvc Constant voltage characteristic setting signal EV Voltage error amplification circuit Ev Voltage error amplification signal ID Output current detection circuit Id Output current Detection signal INV Main power supply circuit MPC External characteristic inclination setting circuit Mpc External characteristic inclination setting signal MPT Welding prevention period setting circuit Mpt Welding prevention period setting signal SC Main control circuit Sc Main control signal SW Switching circuit TS Start circuit Ts Start signal VD Output voltage Detection circuit Vd Output voltage detection signal VS Output voltage setting circuit Vs Output voltage setting signal

Claims (1)

  When a welding end command is input to the welding power source, a stop command is output to the motor, and consumable electrode arc welding that performs anti-stick control of the welding power source output so that the wire burn-up height when the welding wire stops reaches a predetermined value. In the welding prevention method, a predetermined welding prevention period from the end of the anti-stick control outputs a welding prevention voltage lower than the anti-stic voltage, and the welding prevention period includes a short-circuit reference current in which a short-circuit current is predetermined. A method for preventing welding of consumable electrode arc welding, wherein an external characteristic is formed in which an inclination becomes a positive rising characteristic when less than a value and an inclination becomes zero and a negative flat characteristic when the value is equal to or greater than a short-circuit reference current value.

Images